I bought a custom shelf for my 990 finally. It is about 1/16" too wide and 1/16" too tall. But it looks fine. Here are the dimensions i used to order the rack followed by the dimensions I think will give a better fit.

My Measurements:
Width: 17 3/8"
Height: 7 1/8"
Foot: 23/32"
Depth: 17 11/16"

Better Fit:
Width: 17 5/16"
Height: 7 1/16"
Foot: 25/32"
Depth: 17 11/16"


It would be great though if the outlaws could provide MA a 990 to get the correct measurements for future shelves!

Good luck.
Lou